A conventional power supply can provide multiple output powers to drive different loads through taper of transformer windings or coupling of multiple windings. For instance, R.O.C. patent No. M244645 entitled “AC distributed power supply” provides a power supply structure in FIG. 2 thereof and a circuit diagram in FIG. 5 showing a transformer equipped with multiple windings to provide multiple outputs at different voltages. However, study and tests indicate that multiple outputs through multiple windings generate more loss and reduce electric energy transformation efficiency. Now research and development in the industry focus on an approach that provides single main output power first from a rear end of the transformer, and has at least one voltage regulation output unit to receive the main output power and regulate to deliver secondary output power different from the main output power. FIG. 1 illustrates such a technique in which the power supply receives input power from a power source 1. The input power passes through a power factor correction unit 21 to supply a main power system and a standby power system 25. The standby power system 25 receives the input power and outputs standby power. The main power system includes a transformer 24 and a pulse width modulation unit 22 to drive a switch 23 to regulate the period of the input power passing through the transformer 24. The secondary side of the transformer 24 generates induction power which is regulated by a rectification output unit 3 to become the main output power sent to a main output end 5. After the rectification output unit 3 has received the induction power, the main output power is formed by going through a voltage boosting process. The duration of boosting the voltage from an initial voltage to a rated voltage is called rise time. The rectification output unit 3 has a rear end connecting to two voltage regulation output units 41 and 42 that have respectively a secondary output end 411 and 421, a power input end 412 and 422 and a biased driving end 413 and 423. After the biased driving ends 413 and 423 have received the main output power, the voltage regulation output units 41 and 42 regulate the main output power received from the power input ends 412 and 422 to become the secondary output power delivering through the secondary output ends 411 and 421. The two voltage regulation output units 41 and 42 may generate the secondary output power at different potentials. Although the structure depicted in FIG. 1 can improve electric energy transformation efficiency, output time series of the main output power and the secondary output power are different. While such a difference does not create problems for most loads, it could cause start failure of a computer motherboard when in use. The existing of the output time series difference is an issue remained to be resolved.